A 22-year-old nursing student faints every time she undergoes venipuncture. The syncope of blood-injection-injury phobia is characterised by which haemodynamic pattern?

• A Sustained sympathetic activation with persistent tachycardia and hypertension
• B Initial rise in heart rate and blood pressure followed by vagally mediated bradycardia and hypotension ✓
• C Immediate fall in vascular resistance without any change in heart rate
• D Progressive volume depletion leading to orthostatic hypotension

Explanation

Blood-injection-injury phobia produces a unique biphasic vasovagal response: brief sympathetic activation raises heart rate and blood pressure, followed by excessive vagal outflow causing bradycardia, peripheral vasodilation, and syncope. This explains why these patients faint rather than simply feel anxious, unlike other phobia subtypes. Option A describes a pure sympathetic state seen in panic, and option D describes true orthostatic hypotension, neither of which accounts for the fainting.

Reference: Kaplan and Sadock's Synopsis of Psychiatry, 12th ed.

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